1. Field
The embodiments discussed herein relate to a piezoelectric component with directly structured external contacting, a method for manufacturing the component and use of said component.
2. Description of the Related Art
Piezoelectric components are used, for instance, within automotive engineering for activating fuel injection valves. The core of these components is a piezoelectric element, in which an electrode layer and an additional electrode layer are arranged one above the other. A piezoelectric layer is disposed between the electrode layers. The piezoelectric layer consists, for instance, of a piezoceramic, such as lead zirconate titanate (PZT). Activation of the electrode layers with different electrical potentials causes an electrical field to couple into the piezoelectric layer. The coupled electrical field results in a deflection (expansion and/or contraction) of the piezoelectric layer and, thus, of the piezoelectric element.
To achieve as significant a deflection as possible at the same time as as high a force transmission as possible, the piezoelectric components are configured in a multilayer structure. In this way a plurality of piezoelectric elements is arranged one above the other to form a piezoelectric element stack. In the piezoelectric element stack, electrode layers (inner electrodes) and piezoelectric layers are arranged alternately one above the other.
A so-called multilayer capacitor structure (comb structure) is usually realized for contacting the electrode layers. In this way, the electrode layers are guided alternately to different side faces of the piezoelectric element and thus to different side faces of the piezoelectric element stack and are electrically contacted there. In the event in particular of monolithic piezoelectric element stacks, it is problematical here that the electrode layers do not delimit the entire surface of the piezoelectric layer arranged therebetween. The arrangement which is not over the entire surface results in piezoelectrically active and piezoelectrically inactive regions. Different electrical fields are coupled into these regions. The different electrical fields result in different deflections and thus in mechanical stresses. These mechanical stresses generally result in cracks. The cracks themselves can be tolerated. They nevertheless result in a significant outlay in terms of an external electrode attached to the side face of the piezoelectric element stack for electrical contacting of the electrode layers.
The so-called fully active piezoelectric actuator represents an alternative variant. With this piezoelectric actuator, the electrode layers and the additional electrode layers delimit the entire surface of the piezoelectric layers arranged therebetween. As a result, an essentially identical electrical field is coupled into the overall piezoelectric layer. This results in hardly any mechanical stresses and cracks resulting therefrom developing. However, it is necessary for the electrode layers to be individually electrically activatable. Care must be taken to ensure that corresponding electrical potentials can be applied to the electrode layers independently of one another.